The present invention relates to fracturing operations and, more particularly to, methods of forming highly conductive pillars and channels in propped fractures.
Various methods are known for fracturing a subterranean formation to enhance the production of fluids. In a hydraulic fracturing operation, a pressurized fracturing fluid can be used to hydraulically create and propagate a fracture within the subterranean formation. Fracturing fluids can also carry and deposit solids such as proppants into the fracture. Inside the fracture, the proppants can form a tightly packed permeable mass (sometimes referred to as a “proppant pack”). The proppant pack serves as a physical barrier that prevents the fracture from fully closing and as a conduit through which production fluids can flow. The degree of success of a fracturing operation depends, at least in part, upon the fracture conductivity once the fracturing operation is stopped and production is begun. The conductivity of these proppant packs are somewhat limited because of the relatively small interconnected interstitial spaces between the packed proppant.
Another fracturing approach involves placing a much reduced volume of proppants in a fracture in order to create a high porosity fracture. In such operations, the proppant particulates within the fracture may be widely spaced but still present in an amount sufficient to hold the fracture open and allow for production fluids to flow. An increased fracture conductivity may result due to the fact that the produced fluids may flow around widely spaced proppant rather than through the relatively small interstitial spaces in a proppant pack. While this fracturing concept has been investigated in the industry, its widespread usefulness is still somewhat limited for a number of reasons. Among other things, settling of proppant can be particularly problematic when fracturing with a reduced volumes of proppants are used. Proppant settling may lead to a fracture or a top portion of a fracture closing, which can lower the conductivity of the propped fracture and result in proppant aggregation, rather than discrete proppant pillars.